1. Field of the Invention
The present invention relates to a technique to process the gradation characteristic of image data based on a tone curve in an image forming apparatus and an image control program.
2. Description of Related Art
In order to obtain print output matters desired by a user, a tone curve which shows output density relative to input density is set up based on a user's designation in a host device, such as a personal computer. Then, it is possible to perform gradation correction (γ correction) of image data by use of the set-up tone curve. Here, the tone curve means a conversion curve used to convert the characteristic of an image.
However, in order to obtain the print output matters in the actually-desired state, the adjustment of this tone curve requires sensitive operations. Accordingly, as described in the following patent documents, techniques to apply various devisals are proposed.
JPA (Japanese Unexamined Patent Publication) No. 9-69945 Official Report, proposes devisals at the time of display of image applied with an adjusted tone curve on a screen. JPA 2000-115537 proposes devisals to enable fine adjustment on the state that a part of a tone curve is enlarged. Further, JPA 2009-037398 proposes a technique to receive a tone curve set up or adjusted by a host device and to adopt (apply) the tone curve at an image forming apparatus side.